1. Field of the Invention
This invention relates to a process of preparing a polyamide, i.e. nylon, from a diamine, a dinitrile and water.
2. Description of the Prior Art
Commercial processes for preparing nylons, which use diamines and dicarboxylic acids as raw materials, are well known in the art. For example, it has been proposed that linear polyamides can be made by heating a reaction mixture comprising a dinitrile, a diamine and water. This process is disclosed in Greenwalt U.S. Pat. No. 2,245,129. The procedure disclosed in the Greenwalt patent is carried out in two stages, the first stage comprising the heating of the reaction mixture in a closed reaction vessel until a low molecular weight polyamide is formed, and the second stage comprising subsequent heating of this low molecular weight polyamide (i.e. precursor or prepolymer) to form a higher molecular weight polyamide.
Another process for preparing high molecular weight polyamides comprising contacting a dinitrile, a diamine and water is taught in Onsager, U.S. Pat. No. 3,847,876. The Onsager process requires at least equimolar amounts of the diamine and dinitrile to be initially present in the reaction vessel. Also Onsager requires that polymerization occur in the presence of controlled amounts of ammonia (at least 1 wt %, preferably 3 wt % of the total weight of the diamine, dinitrile and water) which must be maintained by the addition of ammonia to the reaction mix.